Luminair



LUMINAIR Filed March 14, 1935 INVENTOR. T homas W Ralph A TTORNE Y.

Patented Dec. 1,1937 2,101,199 2 UNITED STATES PATENT OFFICE LUMINAIR Thomas W. Rolph, Newark, Ohio, assignor to Holophane Company, Inc., New York, N. Y-., a corporation of Delaware Application March 14, 1935, Serial No. 11,006

Claims. (cl. 240-93) The present invention relates to luminairs, and In Figure 1 of the drawing the lamp is shown more particularly to luminairs designed for inat I and the light center at '2. A lens reduces terior illumination and employing a reflector and the spread of light from the light source 2 so that a lens in association with a light source, the lens the virtual center for light emitted from the lens 5 acting on both reflected and direct light. is d. Light rays are shown in light solid'lines. 5

' Lens-reflector combinations heretofore in use Virtual light rays are shown in dash lines. For for interior illumination (as. distinguished from a typical point .5 on the lens, the light ray 2-5 signals, headlights and. the like) have generally from the light center 2 is refracted by the lens used a spherical reflector behind the light source prisms so that it emerges in the direction 5-6,

so that the reflected light falls on the lens at the as if it were emitted from virtual light center i 10 "same angles as the direct light and increases without refraction. Similarly at point I, light emitted light without substantially changing the ray 2-1 from light center 2 is refracted so that spread. The angle through which the spherical it emerges in direction 7-8, the same as if it reflector can be used effectively is limited to the were emitted from virtual light center i. without angle subtended by the lensand hence the spherirefraction. Similarly for typical points 9, l l, i3, 15 cal reflector-lens combination is of limited efli- H5, H1, and it, the light rays from light center ciency. In cases where the reflector has, been 2 are refracted so that they emerge in directions made deep and its contour altered" to allow the 9-!0, ll-l2, l3-I6, I5-II6, l'l-IB and 29-20 light to spread out from the lens, it has been respectively, all as if emitted from point 4.

found that bright spots and undesirableappear- A reflector form is shown at 2!. The shape 20 ances were obtained at wide angles of view. of the reflector form is such that light ray 2-22 These effects were the result of the reflected light striking the reflector at point 22 is reflected to striking'the lens prisms at undesirable angles. point 5 on the lens. It is refracted by the lens The present invention contemplates a luminair so that it emerges from the lens in direction having a reflector and lens each designed in such 5-23, this direction being at the same angle from 25 a way as to cooperate in giving intensive lighting the normal to the lens as 5-6 which is the direct with a considerably higher efficiency than herelight emerging from point 5. Thus if 5-24 is the tofore available. According to the new design normal to the lens at point 5, the angle 6-5-24 the reflector, which can be prismatic or opaque, is the same as angle 23-5-24. Similarly the reis made deep and the prisms on the lens are arflector contour 2| is such that light my 2-25 0 ranged to properly control both the direct light striking the contour at point 25 is reflected to and the reflected light. point I on the lens and emerges in direction 1-26 In practice it has been found that an effective at the same angle from the normal to the lens as means for securing the high efliciencyfwithcut direct light ray 2-1-8. Similarly for all points undesirable lighting effects comprises a lens reon the contour of the reflector. Typical points 35 ceiving light from a light source and reducing its 21 and 29 are shown with light rays reflected to spread, and a cooperating reflector also receiving points 9 and II on the lens at angles such that light from the light source and directing it to the emerging light rays 9-28 and "-30 are at the lens at angles such that the distribution of the same angle from the normal to the lens as 40 light obtained from the lens is the same with light rays 9-! and ll-l2 respectively. 40 direct light and with reflected light, the only From the geometry of this construction it will difference being that from any point on the lens, be clear that light rays reflected by the reflector direct light is delivered on one side of a line and refracted from the lens will come toa focus drawn through said point and parallel with the I at point 3| below the lens, the distance or point axis of the system, while reflected light is deliv- 3| below the lens being the same as the distance 45 ered on the other side of the same line. of virtual light center 4 above the lens. There- The accompanying drawing shows, for purposes fore, the entire construction will deliver light of illustrating the present invention, two of the from two virtual light centers, 4 and 3|, and the many embodiments in which the invention may light distribution obtained from these points take form, it being understood that the drawing will be identical. 50 is illustrative of the invention rather than limit- In any cross-section through the complete coning the same. struction, the lefthand side of the lens will be In the drawing: delivering light received directly from the lamp Figures 1 and 2 are sectional views through and emitted in apredetermined light distribution 5 luminairs embodying the present invention. directed toward the left of the center or the lens.

The same lefthand side of the lens willbe receiving light reflected from "the reflector and emitted from the lens in exactly the same predetermined light distribution, but with sign reversed, so that it is directed toward and across the axis of the lenssr In actual practice when such a construction as this is used in rooms of usual ceiling height, the diflerence in position of virtual light" centers t and 3| becomes negligible so that in effect the same lighting result is obtained from both centers. At any point in a room the near side of the lens is delivering light received by the lens directly from the light source and refracted to the given point, while the far side of the lens is delivering light reflected from the reflector and then refracted by the lens toward the same point in the room.

In previous combinations of lenses and refiectors (such as above referred to) it has been customary to use a spherical reflector back of the lamp. Such a reflector reflects the light back onintercept only a small part of the light going upward from the lamp. The rest of the light included in angles 5-2-32 and ill-2-33, cannot'be reflected to the lens to be refracted into directions desired and hence such constructions are necessarily inefllcient. It will be apparent that the new construction described above can use a deep reflector intercepting practically all of the light which is not caught by the lens direct.

The reflector not only intercepts such light but returns it to the lens in directions such that the reflected light is emitted from the lens in exactly the same light distribution as the direct light. Thus high efliciency and correct light distribution is obtained. v

The reflector may beat any material whatever giving specular reflection of light such as polished metal, mirrored glass, reflecting prisms, etc. Even diffusely reflecting material insofar as it has a specularly reflected component will operate in accordance with the idea of this construction. The lens is usually of Fresnel or stepped outline, although in some instances a double convex lens may be used.

The above is a description of. the construction in its simplest geometrical form. Many variations may be introduced to satisfy varied requirements from the standpoints of light disin this figure, but maybe such that there is no one. point which is its virtual light center. In a typical case of this kind, the virtual light center for various directions of light required at the various angles from the vertical may move back and forth between points like point. 3d and point 35. In this case, the locus of the virtual light center will be the line connecting points as and 35. The lens will be designed to give this exact light distribution; thenthe reflector will be designed to give the same light distribution with the reflected light directed by the lens toward the opposite side of the lens axis. The

principle involved will be the same and all the advantages obtained will be the same but the distribution instead of being the distribution which may result from a single'center 4 will be an exact distribution having no definite center point such as 43, on the lens the prisms spread the direct light 40-43at a certain angle such as 63a one side of the vertical and the reflected light flll-M-dS at the equal angle 43b on the opposite side of the vertical. The direct light is depressed slightly by the lens prisms while the reflected light is elevated by the same prism and leaves the lens at the same angle on the opposite side of the vertical. Similarly at point 45 on the lens which happens to be a point where prism angles change direction. Here the direct light goes straight through and the reflected light goes straight through, the design being such that these two light rays leave at the same angle from the vertical but on opposite sides. Similarly for other points on the lens. In this design, the lens prisms outside of 45 are depressing prisms while the lens prisms inside of 45 are elevating or spreading prisms. 46 is a point on the lens inside of point 45 and hence the prism at 46 elevates slightly the light direct fromthe lamp and depresses slightly the light reflected from the reflector.

,A lens like that illustrated in Fig. 2 does not produce a virtual light center at a point such as point 4, Fig. 1. In the cross-section shown in Fig.' 2, the left-hand side of the lens produces a virtual center for the direct light at point 41 and the right-hand side of the lens produces a virtual center for the direct light at point 48. The construction of the reflector to cooperate with the lens brings the reflected light from the left-hand side of the lens to a focus or point 49. This is located below the lens a distance equal to the distance point 51 above the lens. The reflected light from the right-hand side oi the lens would come to a focus at a point corresponding to 49 but on-the other side of the axis of the system.

Where the prisms are concentric, the virtual center will move around in a horizontal ring or circle of which points 41 and 48 are two opposite points on the circumference. Just as in Fig. 1, it was stated that the virtual center might not be a point but might be a locus on the line 34-35, so in Fig. 2, the locus of the virtual center is a horizontal circle whose diameter is the line 41-48. Therefore, the lens brings reflected light to a focus ina ring or circle the same size as circle 41-48 but located below the lens at a position exactly corresponding to 41-48 above the lens. $9 is one point on this lower circle.

The reflector is designed to cooperate exactly with this lens so that no matter what the lens prisms at any one point are doing, the light emitted from that point will always include light from the lamp emitted on one side of the normal and light from the reflector emitted at exactly the same angle on the other side of the normal.

Where a substantially point light source is employed the reflectors of Figures 1 and 2 will be annular and the lens plates will have concentric prisms. Where a long light is employed the re given would then refer to lens are designed to do aromas flectors will be trough shaped and the lens plates 2. series of parallel prisms. The description above a typiml 1-1 verse section.

With this new design one can use a reflector as deep as desired because the prisms on the the right thing to both the reflected light and the direct light. The only limit in depth of reflector is that, in case of a square lens, it must be scan? far enough above the lens to allow direct light to reach the corners of the lens for reasons of appearance. If the lens were round, the reflector could be carried right down to contact with the lens.

This great depth of reflector tends to increase lens emciency materially. Furthermore, the reflector shape itself is one which is more cient than a spherical shape, first because it returns less light through the lamp bulb itself and second because prismatic reflectors act more emcientiy when light strikes the surface at an angle than when light strikes the surface normally.

Luminairs constructed as herein shown are specially well adapted for flush mounting and for use in general illumination. They give a sumcient spread of close spacing at ordinary mting heights.

What is claimed is:

1. A luminair comprising a light source, an open-mouthed reflector about the light source and a prismatic light transmitting-memberdisposed across the mouth of the reflector to intercept direct and reflected light and reiractively transmit the same, the reflected light being received by the prismatic member at a difierent angle from the reflector axis than that of the incident on the same area of the substantially the same angular divergence from the reflector axis as that of the direct light refracted from said point and on the opposite side of the axis.

, 2. A luminair as claimed in claim. 1, wherein to avoid the expense ofsaid include outer light concentrating prisms and inner light ng prisms- 3. A luminair as claimed in cl 1, wherein each cross-section of the construction delivers from the prismatic transmitting member a given light distribution with virtual center above the member and made up of light direct from the lamp and the same distribution with virtual center below the member and t. up of light directed from the reflector.

a. A luminair comprising a light source, an open'mouthed light converging reflector about the light source and a flat light tmitting and refracting member disposed across the mouth of the reflector and positioned in relation thereto so that the reflected light is received by the member at a different angle from the normal to the said member than that of the direct light incident on the same area of the transmitting member; said member being provided with prisms of variant refractive power to retract said reflected light to emerge at each point at substantially the e angular divergence from the no it mitting met. at that point as that of the direct light refracted from said point and on the opposite side of the normal at said point.

5. A luminair comprising a light source, an annular reflector about the light source having a cross section to converge reflected rays td the reflector axis beyond the mouth of the reflector, and a coaxial lens having annular prisms of variant refractive power, each prism. intercepting the diverging direct light and retracting it in a manner to decrease the divergence thereof so that the virtual source of the direct light is substantially along the axis but further from thelens than the true source, each prism of the lens retracting the reflected light toward the axis to increase the convergence thereof so that the virtual source of the reflected light is substantially along the axis, the lens being substantially equidistant from the two virtual sources.

a to the trans- 

